Paulrud CO, Clausen S, Andersen PE, Rasmussen MD: Infrared thermography and ultrasonography to indirectly monitor the influence of liner type and over- milking on teat tissue recovery. Acta vet. scand. 2005, 46, 137-147. – Eight Danish Holstein cows were milked with a 1-mm thick specially designed soft liner on their right rear teat and a standard liner mounted under extra high tension on their left rear teat. Four of the animals were overmilked for 5 min. Rear teats were subjected to ultrasound examination on the first day and to infrared thermography on the second day. Teats were submersed in ethanol 20 min post-milking on the second day. Ultrasonography mea- surements showed that teat canal length increased by 30-41% during milking. Twenty minutes after milking, teats milked with modified standard liners still had elongated teat canals while teats milked with the soft liner were normalized. Overmilking tended to in- crease teat wall thickness. Approximately 80% of variability in teat canal length, from before teat preparation to after milking, could be explained by changes during teat preparation. Thermography indicated a general drop in teat temperature during teat preparation. Teat temperature increased during milking and continued to increase until the ethanol challenge induced a significant drop. Temperatures approached pre-chal- lenge rather than pre-milking temperatures within 10 minutes after challenge. Teat tem- peratures were dependent on type of liner. Mid-teat temperatures post-challenge relative to pre-teat preparation were dependent on overmilking. Thermography and ultrasound were considered useful methods to indirectly and non invasively evaluate teat tissue in- tegrity. Dairy cow; milking, teat integrity, thermography, ultrasound. Acta vet. scand. 2005, 46, 137-147. Acta vet. scand. vol. 46 no. 3, 2005 Infrared Thermography and Ultrasonography to Indirectly Monitor the Influence of Liner Type and Overmilking on Teat Tissue Recovery By C. O. Paulrud 1 , S. Clausen 2 , P. E. Andersen 2 and M. D. Rasmussen 1 1 Danish Institute of Agricultural Sciences, Research Centre Foulum, DK-8830 Tjele, Denmark, 2 Risoe National Laboratory, DK-4000 Roskilde, Denmark. Introduction Several scientific publications deal with the acute response of teat tissue to machine milking (McDonald 1975, Schultze & Bright 1983, Hamann & Dück 1984, O'Shea 1987, Persson 1991, Bramley et al. 1992). Hamann (1989) pointed out the various degrees of altered teat tissue fluid-dynamics as a significant reason why milking may have a negative effect upon teat defence mechanisms. There is general agreement that machine milking can result in congestion and oedema of the teat tissue espe- cially at the teat end and also influence teat di- ameter, penetrability of the teat canal, and de- fence mechanisms. The functional effect of impaired teat fluid cir- culation may be divided into firstly, effects con- cerning teat canal closure and passage of pathogens, and secondly, possible effects on the immunological defence mechanisms concern- ing antigenic detection and initiation of im- munological responses. Hillerton et al. (2002a) found overmilking to be associated with poor teat condition. Further- more, avoidance of overmilking was pointed out to be essential in order to accomplish good parlour performance and acceptable cow com- fort (Hillerton et al. 2002b). Natzke et al. (1982) on the other hand reported no apparent effect on external teat end condition but an in- creased rate of new infections among over- milked cows and concluded that the higher new infection risk was associated with increased rates of cross infections, presumably due to in- creased unit-on time. This hypothesis was sup- ported by Mein et al. (1986) who found an in- creased new infection rate when pulsation failed especially in conjunction with overmilk- ing and that overmilking increased new infec- tion rate mainly or only when it was associated with pulsation failure. The vacuum applied during the milking phase of machine milking disturbs the naturally oc- curring teat contractions and results in accumu- lation of fluid in the teat tissue. These contrac- tions normally remove interstitial fluids from the teat via the lymphatic vessels. During the massage phase, however, teats will be massaged by a compressive load that facilitates venous flow and removal of interstitial fluid (IDF 1987). During periods when the milk flow is low or none, the existing removal of blood and interstitial fluids may be insufficient and con- gestions and oedema may develop (IDF 1987). Jankus & Baumann (1986) examined the blood flow through the distal parts of the teat and found that the blood flow through the teat canal epithelium and the papillated portion of the stratum papillare were 4 times that of equiva- lent structures of the mucosal (Furstenberg's) rosette. They suggested two factors that may account for the high blood flow: 1) The secre- tion of antimicrobial substances, and/or 2) The requirement for cellular replacement due to ep- ithelial stratum corneum losses during milking. A number of methods to measure teat tissue condition have been introduced. Ultrasonogra- phy of teats in order to measure teat congestions may be the most frequently used method (Worstorff et al. 1986, Spencer et al. 1996). Other methods used to study the microcircula- tion and integrity of teats include Laser doppler flowmetry (Persson 1991, Hamann et al. 1994), teat consistency by cutimeter or caliper mea- surements (Hamann & Mein 1988), radio- graphic methods (Pier et al. 1956, McDonald 1975, Mein et al. 1973) and different methods of measuring teat surface temperature (Ha- mann & Dück 1984, Hamann 1985 & 1988, Eichel 1992, Ordolff 2000). Ultrasonography permits a visualisation of body structures by recording the echoes of con- tinuous pulses of ultrasonic (1-10 MHz in diag- nostic ultrasonography) waves directed into the tissue. Those frequencies can be transmitted only through liquids and solids and conse- quently teat ultrasonography is performed through a contact gel or by immersing the teat into water. Skin temperature can be used in order to esti- mate tissue integrity since it reflects the under- lying circulation and tissue metabolism. In or- der to avoid any skin contact and to increase the study area and time efficiency, infrared ther- mography has been adopted to study tempera- ture patterns of udder and teat skin (Hamann & Dück 1984). Thermography is based on the principle of the Stefan-Boltzmann law whereby the energy flux emitted by a surface is related to its temperature. Thermography focuses, col- lects and transforms the infrared range of the electromagnetic spectrum that is emitted from any body in a heat dependent fashion. Ther- mography furthermore images a pictorial sum- mary of the heat gradients generated and can thereby visualise the thermal patterns of the skin resulting in useful mapping of the underly- ing circulation. The generally high degree of thermal symmetry in healthy animals makes it 138 C. O. Paulrud et al. Acta vet. scand. vol. 46 no. 3, 2005 possible to detect subtle, abnormal asymme- tries. Generally, teat integrity may be assessed either by comparing the actual temperature or relative temperature between adjacent teats or comparing the teat's ability for circulatory re- sponse to a certain challenge. The objectives of this study were: First, to study the influence of certain liner characteristics and overmilking on teat recovery by indirectly mon- itoring circulatory impairments of teat tissue via infrared thermography and ultrasound scan- ning. Second, to compare responses measured by infrared thermography and ultrasound scan- ning. Materials and methods Eight Danish Holstein cows from the herd at the Research Centre Foulum were milked experi- mentally in a combined group and split udder design. Cows were diagnosed as being free of clinical mastitis for at least 4 weeks before the start of the experiment. In addition, rear teats had similar size and shape and deposited milk in a similar fashion (time span). In order to per- form and compare both infrared thermography and ultrasound scannings, the same individuals were milked identically during two consecutive afternoon milkings. Cows were housed in a tie-stall, manually stim- ulated for 30 seconds with a moistened cloth and manually foremilked. Cows were machine- milked with a high pipeline milking system, a SAC Uniflow milking unit, a milk line vacuum of 48 kPa, 60 c/min and a 60:40 pulsation ratio. On their right rear teat, the cows were milked with a 1-mm thick, soft, experimental liner (soft liner) with a mouthpiece only 5 mm high. On their left rear teat, the cows were milked with an SAC (S A Christensen, Kolding, Denmark) No:15012 liner (extended liner) mounted under extra high tension in a 12-mm extended stan- dard shell, resulting in a 30-mm mouthpiece height. Both front teats were milked with stan- dard mounted SAC-15012 conventional liners. Only data from rear teats were recorded. Cows were randomly divided into two groups. Four animals were milked with the automatic cluster remover set at a threshold of 300 g/min while the remaining four animals were milked excessively for 5 min to simulate overmilking. On the first day of experimental treatment, the rear teats were subjected to ultrasound exami- nation pre-teat preparation (PRP), post-teat preparation (POP), immediately after milking (AM), and 20 minutes post-milking (AM+). Ultrasonographic scans were carried out with an ALOKA Echo Camera model SSD-500 mounted with a 7.5 MHz ultrasound probe by submerging teats in a water-filled (35°C) plas- tic cup as described by Spencer et al. (1996). Images were stored on a video recorder. On the second day, the animals were milked as on day one. Thermographic images (Raytheon, "Radiance PM", focal array camera, 256×256 pixels and a sensitivity of about 0.025°C) of the rear teats were taken pre-teat preparation (PRP), after teat preparation (POP), immedi- ately after milking (AM), and 20 minutes after milking (AM+). Then the teats were challenged by a quick submersion in ethanol. The teats were thereby cooled as a consequence of ethanol evaporating and changing function of state from liquid to gas. Excessive cooling of the teat tip was avoided by removing a drop of ethanol at the teat tip with a cloth. A series of fi- nal thermographic images were taken 2, 5, and 10 minutes after challenge (C+2, C+5 and C+10, respectively). Temperatures were recov- ered by processing the thermographic images in AmberTherm software (Amber, USA) Temper- atures were recorded at the centre of the teat tip, at the mid-teat, and at the centre of the teat base. The ambient temperature at time of thermogra- phy was 19ºC. Ultrasound measures of the thickness of the teat cistern wall, teat cistern diameter and the teat Infrared thermography and ultrasonography to monitor teat tissue recovery 139 Acta vet. scand. vol. 46 no. 3, 2005 canal length as well as temperatures derived from the thermographic pictures at teat tip, mid-teat and teat base were compared between treatments. Results from ultrasound were com- pared to those from thermography. Data analysis The absolute and relative temperatures were analysed by the following model using the sta- tistical procedure PROC MIXED (SAS, 1999): Y = LINER + OVERMILKING + TIME + PO- SITION + LINER × OVERMILKING + LINER × TIME + OVERMILKING × TIME · Random effects: COWNR × OVERMILKING · Repeated: LINER(COWNR) LINER was the effect of the two different milk- ing machine liners. OVERMILKING was the effect of overmilking for 5 minutes or not. TIME was whether data was collected pre- preparation, after preparation, 0 and 20 minutes after milking, and 2, 5 and 10 minutes after challenge. POSITION was the effect of loca- tion at the teat: base, mid and teat tip. Ultra- sound measures of the thickness of the teat cis- tern wall, teat cistern diameter, and teat canal length were analysed using the same model but leaving out the term POSITION. Data are pre- sented as Least Squares Means. Results Teat skin temperature Teat skin temperatures were dependent on the position on the teat and the time of measure- ment but not on overmilking, Table 1. Teat skin temperature decreased significantly from teat base to mid-teat and from mid-teat to teat tip (p<0.001), Table 2. After milking, overall teat temperatures were significantly dependent on the type of liner (AM p<0.05 and AM+ p<0.001). Even though differences in teat tem- perature between liners were small (table 2), milking with the soft liner resulted in colder teats than milking with the extended liner. Also after the ethanol challenge, the overall teat tem- perature was significantly dependent on the type of liner (C+2: p<0.05; C+5: p<0.01; and C+10: p<0.001) but independent of overmilk- ing. The most obvious response to different lin- ers was recorded 10 minutes post-challenge where temperatures at both teat tip, mid-teat and teat base were significantly lower on teats milked with soft liners, Table 2. 140 C. O. Paulrud et al. Acta vet. scand. vol. 46 no. 3, 2005 Table 1. Least Squares Means of temperatures of teats milked with extended and soft liner, respectively, and overmilked or not. Temperatures were taken from pre-teat preparation, after preparation, immediately after milk- ing, 20 minutes after milking, and 2, 5, and 10 minutes after an ethanol challenge. Extended Liner Soft Liner Levels of Significance Liner - + - + Position Liner Overmilk Overmilking (n=12) (n=12) (n=12) (n=12) Pre-Preparation 34.4 33.8 33.8 33.8 *** Post-Preparation 32.5 32.7 32.3 32.1 *** Milking +0 min. 35.2 34.9 34.3 34.2 *** * Milking+20 min. 35.3 35.6 34.6 34.9 *** *** Challenge +2 min. 33.0 32.9 32.0 32.4 ** * Challenge +5 min. 34.7 34.7 34.1 34.1 *** ** Challenge +10 min. 34.8 35.6 34.1 34.8 *** *** Statistical differences are designated with *, **, or *** for 5, 1, and 0.1 percent significance levels, respectively. Relative temperatures There was a general drop in teat temperature of about 1.5ºC from pre- to post-teat preparation (p<0.001), but this drop was independent of po- sition at the teat (p=0.76), Table 3. When com- paring temperatures after milking with pre-teat preparation, an effect of position was evident (p<0.01). Preparation of the teat affected teat temperature evenly while milking affected teat temperature differently at different areas of the teat. No effect of liner or overmilking was estab- lished on the temperatures post-milking in rela- tion to pre-teat preparation. At the middle, overmilked teats were 1.1ºC and 1.7ºC warmer 5 and 10 minutes post-challenge, respectively (p<0.05 and p<0.01, respectively) than pre-teat preparation while mid-teats that were not over- milked were only <0.1ºC and 0.3ºC warmer than pre-teat preparation, respectively. Ten min- utes after challenge, the overall teat tempera- ture and teat base temperature in relation to pre- teat preparation were significantly dependent on type of liner (p<0.01 and p<0.05, respec- tively), Table 3. Ten minutes after challenge, the overall teat temperature in relation to pre-teat preparation tended to be higher among over- milked teats than among the other teats (1.4ºC and 0.4ºC, respectively, p=0.06). Infrared thermography and ultrasonography to monitor teat tissue recovery 141 Acta vet. scand. vol. 46 no. 3, 2005 Figure 1. Infrared thermography of four different udders taken between hind legs immediately after milking. Right rear quarters were milked with a soft experimental liner and left rear quarters were milked with a standard liner mounted in an extended shell. Table 2. Least Squares means of teat temperatures of teats milked with extended and soft liners, respectively. Temperatures were taken from pre-teat preparation, after preparation, immediately after milking, 20 minutes af- ter milking, and 2, 5, and 10 minutes after an ethanol challenge. Liner Extended Liner Soft Liner Levels of Significance Teat Position Base Mid Tip Base Mid Tip Base Mid Tip (n=8) (n=8) (n=8) (n=8) (n=8) (n=8) Pre-teat preparation 35.2 34.1 33.1 35.0 33.7 32.7 Post-teat preparation 33.7 32.7 31.4 33.3 32.2 31.1 Milking +0 35.4 35.9 33.8 35.0 35.1 32.6 Milking +20 36.0 35.6 34.7 35.6 34.8 33.8 * Challenge +2 33.3 33.7 31.9 32.6 32.6 31.4 ** Challenge +5 35.5 34.8 34.1 34.9 34.2 33.3 * * Challenge +10 36.1 35.3 34.3 35.2 34.5 33.6 *** *** * Statistical differences between temperatures at three positions of the teats as a result of different type of liner are designated with *, **, or *** for 5, 1, and 0.1 percent significance levels, respectively. Ultrasound measurements of teat dimensions Teat diameter, teat wall thickness and teat canal length were significantly dependent upon time (p<0.001), Table 4. After milking, no statistical differences were found among treatments. Overmilking tended to increase teat wall thick- ness after milking (p=0.066). Generally, after milking, the teats seemed to have a slightly smaller diameter, a somewhat thicker teat cis- tern wall, and a longer teat canal, Table 4. Teat canal length 20 minutes after milking in rela- tion to immediately after milking differed sig- nificantly between liners (p<0.01). Relations between IR- and US-measures The change in teat tip temperatures from pre- teat preparation to 10 minutes after challenge was positively correlated with the change in teat canal length from pre-teat preparation to after milking (p<0.05 and R 2 =0.26). Likewise, the change in overall teat temperature corre- lated positively with the change in teat canal length (p<0.05 and R 2 =0.12). The change in teat canal length during teat preparation was positively correlated with tem- perature changes from pre-teat preparation to 0 and 20 minutes after milking (p<0.001, R 2 =0.80 and p<0.001, R 2 =0.32, respectively). The change in teat wall thickness during teat preparation was positively correlated with tem- perature changes from pre-teat preparation to 20 minutes after milking (p<0.001, R 2 =0.31). Discussion Thermal changes during preparation During manual udder preparation, including pre-stripping and wet cleaning, teat tempera- ture dropped approximately 1.5ºC. This drop in temperature was even throughout the teat sur- face. Hamann & Dück (1984) reported an aver- age decrease in teat temperature of 0.8ºC after pre-stripping, dry cleaning and manually mas- sage of the teat for 30 seconds before milking. Hamann & Dück (1984) hypothesized that prior to manipulation teat veins are filled with blood in order to fill the volume of the teat sinus and reach an occlusion. Then manual stimulation initiates removal of blood from teat veins in or- der to open the occlusion between udder and teat sinus and to increase the volume of the teat sinus. Due to reduced blood volume, the teat wall gets colder and the teat temperature may decrease. A second explanation would be that teat stimu- 142 C. O. Paulrud et al. Acta vet. scand. vol. 46 no. 3, 2005 Table 3. Least Squares Means of teat temperatures in relation to temperatures pre-teat preparation measured at base, mid, and tip of teats milked with an extended liner and soft liner, respectively. Temperatures were measured after preparation, immediately after milking, 20 minutes after milking, and 2, 5, and 10 minutes after an ethanol challenge, respectively. Liner Extended Liner Soft Liner Teat Position Base Mid Tip Overall Base Mid Tip Overall (n=8) (n=8) (n=8) Mean (n=8) (n=8) (n=8) Mean Post-Preparation -1.64 -1.41 -1.45 -1.50 -1.58 -1.45 -1.74 -1.59 After Milking 0.75 1.84 0.75 0.92 -0.13 1.40 -0.04 0.41 Milking +20 1.60 1.48 0.88 1.32 1.13 1.15 0.59 0.95 Challenge +2 -1.12 -0.45 -1.90 -1.16 -1.31 -1.24 -2.40 -1.65 Challenge +5 1.00 0.65 0.11 0.59 0.58 0.50 -0.15 0.31 Challenge +10 1.29 a 1.18 0.89 1.12 x 0.91 b 0.80 0.19 0.63 y ab Numbers with different letters are significantly different (p<0.05) xy Numbers with different letters are significantly different (p<0.01) Infrared thermography and ultrasonography to monitor teat tissue recovery 143 Acta vet. scand. vol. 46 no. 3, 2005 Table 4. Least Squares Means of teat diameter, teat cistern wall thickness, and teat canal length of teats milked with extended and soft liners and overmilked for 5 minutes or not. Measurements were done by ultrasound and given as absolute values or relative to pre-teat preparation (mm). Dimensions are given from pre-teat prepara- tion (PRP), after preparation (POP), immediately after milking (AM), and 20 minutes after milking (AM+). Liner Extended liner Soft liner Overmilking - + - + Level of sign. Absolute values PRP 21.6 22.0 20.4 21.8 POP 21.4 23.2 20.8 22.8 AM 19.2 20.8 19.3 19.3 AM+ 20.3 20.3 20.0 19.7 Relative values POP-PRP -0.2 1.2 0.4 1.0 AM-PRP -2.4 -1.2 -1.1 -2.5 AM+-PRP -1.3 -1.7 -0.4 -2.1 AM+-AM 1.1 -0.5 0.7 0.4 Teat cistern wall Absolute values PRP 5.5 6.0 5.2 6.7 POP 5.4 6.1 5.3 6.8 AM 6.5 9.3 6.5 8.1 + AM+ 7.3 7.9 6.9 8.0 Relative values POP-PRP -0.1 0.1 0.1 0.1 AM-PRP 1.0 3.3 1.3 1.4 AM+-PRP 1.8 1.9 1.7 1.3 AM+-AM 0.8 -1.4 0.4 -0.1 Teat canal length Absolute values PRP 11.4 11.2 11.2 12.9 POP 11.9 11.4 12.5 14.3 ** AM 14.8 14.4 15.8 16.9 * AM+ 13.6 15.0 12.0 13.2 Relative values POP-PRP 0.5 0.2 1.3 1.4 AM-PRP 3.4 3.2 4.6 4.0 AM+-PRP 2.2 3.8 0.8 0.3 AM+-AM -1.2 0.6 -3.8 -3.7 ** Statistical differences between teat properties as a result of different type of liner designated with * or ** and as a result of overmilking are designated with + or ++ for 5 and 1 percent significance levels, respectively. lation will decrease the sympathetic tone of the mammary gland (Lefcourt 1982a) resulting in increased blood flow but, however, also a de- creased rate and amplitude of teat and teat sphincter muscle contraction (Lefcourt 1982b) resulting in decreased blood flow in the teat tis- sue. However, skin blood flow is also under the con- trol of the sympathetic nervous system, and no- radrenergic sympathetic neurons control the blood flow through the teats. During prepara- tion of teats, local extrinsic stimuli as tactile and thermal sensations are registered by mechano- and thermal receptors in the teat skin. Responses evoked by such stimuli are alpha- adrenergic (mediated by adrenergic vasocon- strictor nerves) and include contraction or re- laxation of vascular muscles. A third possibility for teats to be colder after preparation may therefore be activation of the autonomous ner- vous system and an increase in sympathetic tone (alpha-adrenergic response), causing haemodynamic changes including arterioles to contract and arteriovenous anastomoses to close (peripheral vasoconstriction of the local cutaneous vascular plexus). All in all, this re- sults in restricted skin blood flow in the teats and decreased heat dissipation to the surround- ings. Influence of milking on teat temperature While preparation of the teat affected teat tem- perature approximately evenly throughout the teat surface, milking on the other hand affected teat temperature differently at different areas of the teat. The absolute temperatures of the teats after milking and 20 min after milking were sig- nificantly higher of teats milked with the ex- tended than with the soft liner. When compar- ing temperatures post-milking with tempe- ratures pre-preparation, an effect of position was evident (p<0.01). During milking, mid-teat temperature in- creased markedly while both teat base and teat tip temperatures tended to increase less or even slightly decrease with the extended and soft liner, respectively. A decrease in tone as seen during milking causes arterioles and arteriove- nous anastomoses to open, the blood flow to markedly increase, and therefore the convective heat loss from the skin to increase. Hamann & Dück (1984) found that the teat apex and the areas around the annular folds demonstrated the most marked changes in skin temperatures from pre-preparation to post- milking. Teat apex had increased temperatures and teat base had slightly decreased tempera- tures compared to values pre-preparation. When comparing those results to the extended liner in the present trial, we can confirm that teat tip temperature increased during milking relative to pre-preparation. Conflicting results concerning teat base may be explained by dif- ferences in the technical parameters of the milking systems or differences in liner design. Isaksson & Lind (1994) proposed three circum- stances that influenced the temperature condi- tions during milking. First, the milk flow through the teat lumen, second, the enclosure of the teat in the teatcup, and third, the reactions in the cutaneous vascular plexus. These authors pointed out that heat gain is largely balanced by heat loss to the blood stream. If so, one may conclude that the larger the difference is be- tween pre-milking and post-milking tempera- tures, and the longer those differences exist, the more impairments on teat circulation the pro- cess of milking has caused. As mentioned, the present data do not directly measure the blood flow per se but rather the re- sulting temperature. One may, however, specu- late whether the blood flow post-milking is in- fluenced by the requirements for cellular replacement due to epithelial stratum corneum losses during milking and the secretion of an- timicrobial substances, as proposed by Jankus 144 C. O. Paulrud et al. Acta vet. scand. vol. 46 no. 3, 2005 & Baumann (1986). Even though this hypothe- sis seems reasonable, the magnitude of such in- fluence on the present results should be non- significant. Influence of challenge on teat temperature The purpose of introducing a thermal challenge was to investigate whether treatment had any effect on the autonomic nervous system and the vascular system's ability to perform a 'somato sympathetic response'. Immediately after chal- lenge, teat temperature had dropped approxi- mately 2.5ºC on average in relation to before challenge and 1.4ºC in relation to pre-prepara- tion. This drop in temperature may mainly be ascribed to the rapid evaporation of ethanol (en- tropy change) where energy is absorbed from the teat surface. The relative drop in tempera- ture was highest among teats milked with the soft liner (NS). Temperatures measured 5 and 10 min. after challenge seem to approach the values measured 20 minutes post-milking rather than pre-preparation temperatures. This may indicate that machine milking induces long lasting alterations in teat fluid dynamics. Neijenhuis et al. (2001) suggested that the pro- cess of teat recovery, as determined by ultra- sonographic scanning, lasts >8 h. Irrespective of type of liner, overmilked mid- teats were 1.1ºC and 1.7ºC warmer at 5 and 10 min. after challenge, respectively, than before preparation while mid-teats that were not over- milked were only <0.1ºC and 0.3ºC warmer, re- spectively, than before teat preparation. Over- milking therefore seems to result in prolonged teat recovery time and perhaps reduced ability to perform a 'somato sympathetic response' to the challenge. Temperatures relative to pre- preparation of teats milked with the extended liner at 10 min. after challenge were about twice that of teats milked with the soft liner. Therefore one may conclude that teats milked by soft liners have shorter recovery time and perhaps increased ability to perform the 'so- mato sympathetic response' than did teats milked with the extended liner. Results from Rasmussen et al. (in progress) comparing dif- ferences of teat condition post-milking confirm a significant difference between the very same two liners as used in the present experiment. They found that milking with the experimental liner reduced ringing of the teat base, teat con- dition scores after milking, and anatomical changes associated with milking studied by ul- trasound. The mentioned parameters are all as- sociated with circulatory impairments of the teat, as is the reduced ability to perform a rele- vant 'somato sympathetic response'. Conse- quently teats with consistent differences in teat temperatures compared to pre-milking may have reduced ability to regulate the blood flow through the cutaneous vascular plexus. Ultrasonography The teat diameter decreased independently of treatment during milking but was 6-13% smaller after milking. Teat canal length in- creased by 30-41% during milking. Twenty minutes after milking, teats milked with the ex- tended liner still had elongated teat canals while teats milked with the soft liner had teat canal lengths non-significantly different from pre- teat preparation. This stands in contrast to Nei- jenhuis et al. (2000) who claim an increase in teat diameter of about 12% and an increase of only about 10% in teat canal lengths from pre- teat preparation to after milking. Teat wall thickness did not respond to treatment but did generally increase by 20-50% during milking. This result confirms the results of Neijenhuis et al. (2001) who found an average increase of 34% in teat wall thickness from pre-preparation to after milking. Our results show that approximately 80% and 32% of the variability in the changes of teat canal length from pre-teat preparation to 0 and Infrared thermography and ultrasonography to monitor teat tissue recovery 145 Acta vet. scand. vol. 46 no. 3, 2005 20 minutes after milking, respectively, could be explained by changes occurring during teat preparation. If teat preparation and milking are performed as in the present experiment, it is possible, with fair accuracy, to estimate teat canal elongation from before teat preparation to immediately after milking and 20 minutes after milking. Since the change in teat canal length from immediately after to 20 min. after milking was significantly dependent on type of liner, one may suspect that the impact of the type of liner may have reduced the linear relationship of elongation during teat preparation and that occurring during milking. Implications and conclusions Somewhat surprisingly, the actual teat tempera- ture seems to be more dependent on type of liner than the temperature relative to pre-teat preparation. Therefore, pre-teat preparation temperatures may possibly be left out when comparing liner impact on teats. Thermography can be a very useful tool to eval- uate, estimate and differentiate short and longer-term tissue reactions to machine milk- ing. Our results stress the importance of teat measuring position and the liner specific tissue alterations. Milking-induced changes of both teat canal length and teat wall thickness could be pre- dicted by changes during teat preparation but still be dependent on type of liner. Conse- quently, teats vary in sensitivity or level of re- sponse. Despite somewhat conflicting results, our find- ings support the suggestion by Neijenhuis et al. (2001) that ultrasound measurement of teat pa- rameters is a useful tool for studying changes in teat properties caused by milking. The present work did not fully clarify how ul- trasonographically assessed teat tissue parame- ters correspond to thermografically estimated teat temperatures even though some interac- tions were claimed. Further research may take us closer to the obviously complicated interplay between milking-induced intercellular fluid al- terations, circulatory impairments, and teat de- fence mechanisms. We gratefully acknowledge the financial sup- port of the Danish Dairy Board, Aarhus, Den- mark for this project. References Bramley AJ, Dodd FH, Mein GA, & Bramley JA, ed: Machine Milking & Lactation, Insight Books, Birkshire, VT. Eichel H: Zum Verhalten der Temperatur der Zitzen- haut von Milchkühen, die mit Rohrmelkanlage gemolken wurden, Mh. Vet. Med., 1992, 47, 193- 195. Isaksson A, Lind O: Milking related changes in the surface temperature of the bovine teat skin. Acta vet scand, 1994, 35 (4), 435-438. Hamann J: Zitzengewebereaktionen und maschinel- ler Milchentzug -ein Beitrag zum Infectionsrisiko in der Zwischenmelkzeit, Test issue reactions and machine milking: On the infection risk during the intermilking period. Milchvissenshaft. 1988, 43 (1), 8-13. Hamann J: Infection rate as affected by teat tissue re- actions due to conventional and non-conventional milking systems. Kieler Milchwirtschaftliche Forschungsberichte, 1985, 37 (4), 426-430. Hamann J: Machine milking and new infection risk. Proc. Int. Conf, Mastitis, St Georgen, Austria, 1989, 113-122. Hamann J, Dück M: Erste Untersuchungsergebnisse zur Messung der Zitzenoberfläche unter Verwen- dung der Infrarot-Thermographie. Die Milch- praxis, 1984, 22 (4), 148-152. Hamann J, Mein GA: Responses of the bovine teat to machine milking: Measurements of changes in thickness of the teat apex. J. Dairy Res. 1988, 55, 331-338. Hamann J, Nipp B, Persson K: Teat tissue reactions to milking: Changes in blood flow and thickness in the bovine teat. Milchvissenshaft. 1994, 49, 243-247. Hillerton JE, Pankey JW, Pankey P: Effect of over- milking on teat condition. J. Dairy Res. 2002a, 69, 81-84. Hillerton JE, Ohnstad, I, Baines JR, Leach KA: Per- formance differences and cow responses in new 146 C. O. Paulrud et al. Acta vet. scand. vol. 46 no. 3, 2005 [...]... thermography and ultrasonography to monitor teat tissue recovery milking parlours J Dairy Res 2002b, 69, 75-80 International Dairy Federation: Machine milking and mastitis Bulletin no 215, Brussels 1987 Jankus EF Baumann, LE: Blood flow to the distal , part of the teat (mammary papilla) of lactating dairy cows Am J Vet Res 1986, 47(2), 283285 Lefcourt AM: Effect of teat stimulation on sympathetic tone... mammary gland J Dairy Sci 1982a, 65, 2317-2322 Lefcourt AM: Rhytmic contractions of the teat sphincter in bovines: An expulsion mechanism Am J Physiol 1982b, 242 III, R181-R184 Mayntz B: Preliminary results concerning teat tip consistency and temperature due to linerless and conventional milking Milchwissenschaft, 1990, 45 (5), 291-294 McDonald JS: Radiographic method for anatomic study of the teat canal:... penetrability of bovine pappilary duct to endotoxin after milking Am J Vet Res 1983, 44, 2373-2375 Spencer SB, Griel LC, Goldberg JJ: The use of ultrasonography to measure teat congestion Proceedings, Annual Meeting, National Mastitis Council 1996, 35, 172-173 Worstorff H, Steib JD, Prediger A, Schmidt WL: Evaluation of sectional views by ultrasonics for measuring teat tissue changes during milking of cows... Symposium, Guelph, 1987, 44-65 Persson K: Microcirculation in the bovine teat skin, measured by laser doppler flowmetry Acta Vet Scand 1991, 32 (1), 131-133 Pier AC, Schalm OW, Hage TJ: A radiographic study of the effects of mechanical milking and machine 147 vacuum on the teat structures of the bovine mammary gland JAVMA 1956 129, 347-351 SAS Institute Inc., SAS OnlineDoc®, Version 8, Cary, NC 1999 Schultze... Effects on mastitis of overmilking in conjunction with pulsation failure J Dairy Res 1986, 53, 17-22 Mein GA, Thiel CC Akam DN: Mechanics of the teat and teatcup liner during milking: Information from radiographs J Dairy Res 1973, 40, 179189 Natzke RP Everett RW, Bray DR: Effect of overmilk, ing on udder health J Dairy Sci 1982, 65, 117125 Neijenhuis F Klungel GH, Hogoveen H: Recovery of , cow teats... ultrasonographic scanning J Dairy Sci 2001, 84, 2599-2606 Ordolff D: Oberflächentemperaturen an Euter und Zitze beu konventionellen und automatischen Melkverfahren Surface temperatures of udder and teats for conventional and automatic milking methods Kieler Milchwirtschaftliche Forschungsberichte 2000, 52(1), 5-10 O´Shea J, O´Callaghan E, & Meaney S: Liner slip and impacts Proceedings, International... efter dypning afhang af overmalkningen Det konkluderes, at ultralydsskanning og infrarød termografi er brugbare non-invasive metoder til evaluering af pattekondition (Received March 27, 2003; accepted May 2, 2005) Reprints may be obtained from: M.D Rasmussen, Danish Institute of Agricultural Sciences, Research Centre Foulum, DK-8830 Tjele, Denmark Acta vet scand vol 46 no 3, 2005 ... maskinmalkningens påvirkning af pattekonditionen Otte danske SDM køer blev malket med et 1-mm tyndt specialfremstillet pattegummi på højre bagpatte og med et almindeligt pattegummi monteret i et forlænget hylster på venstre bagpatte Fire køer blev overmalket i 5 min Pattedimensioner blev målt ved hjælp af ultralyd den første dag og pattehudstemperaturen blev målt med infrarød termografi på andendagen Patterne blev... malkningen og var stadig forlænget 20 minutter efter malkning med det almindelige pattegummi, men ikke med specialpattegummiet Overmalkning havde tendens til at øge pattevægstykkelsen Ca 80% af variationen i pattekanallængden fra før forberedelsen til efter malkning kunne forklares ud fra ændringer under forberedelsen Pattehudens temperatur faldt under forberedelsen, blev øget under og efter malkningen, . 2005 Infrared Thermography and Ultrasonography to Indirectly Monitor the Influence of Liner Type and Overmilking on Teat Tissue Recovery By C. O. Paulrud 1 , S. Clausen 2 , P. E. Andersen 2 and M. D Clausen S, Andersen PE, Rasmussen MD: Infrared thermography and ultrasonography to indirectly monitor the influence of liner type and over- milking on teat tissue recovery. Acta vet. scand. 2005,. relation to pre -teat preparation tended to be higher among over- milked teats than among the other teats (1.4ºC and 0.4ºC, respectively, p=0.06). Infrared thermography and ultrasonography to monitor